Vehicle radar system with a shared radar and communication system

ABSTRACT

A shared radar and communications system. The system includes a transmitter and a receiver. The transmitter modules signals based on a first spreading code defined at least in part by a first plurality of information bits. The first plurality of information bits encodes selected information. The transmitter transmits the modulated signals. The receiver receives a first signal and a second signal. The first signal includes the transmitted signals transmitted by the transmitter and reflected from objects in an environment. The receiver processes the first signal to detect objects in the environment. The second signal is transmitted from another system. The second signal carries a second plurality of information bits. The receiver processes the second signal to determine the second plurality of information bits. The second plurality of information bits are encoded with information selected by the other system.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/959,524, filed Apr. 23, 2018, now U.S. Pat. No. 10,536,529, which isa continuation of U.S. patent application Ser. No. 15/496,039, filedApr. 25, 2017, now U.S. Pat. No. 9,954,955, which claims the filingbenefits of U.S. provisional application, Ser. No. 62/327,017, filedApr. 25, 2016, which is hereby incorporated by reference herein in itsentirety.

The present invention is directed to radar systems, and moreparticularly to radar systems for vehicles.

BACKGROUND OF THE INVENTION

The use of radar to determine range and velocity of objects in anenvironment is important in a number of applications includingautomotive radar and gesture detection. A radar system typicallytransmits radio signals and listens for the reflection of the radiosignals from objects in the environment. By comparing the transmittedradio signals with the received radio signals, a radar system candetermine the distance to an object. Using multiple transmissions, thevelocity of an object can be determined. Using multiple transmitters andreceivers, the location (angle) of an object can also be determined.

SUMMARY OF THE INVENTION

Methods and systems of the present invention provide for a shared radarand communication system that simultaneously operates as a radar (fordetecting and estimating location and velocity of objects in theenvironment) as well as a communication system that sends and/orreceives information bits to and from other systems with similarcapabilities. The system operates under a variety of environments, witha variety of external information, and with a variety of objectivefunctions to modify the transmission and reception processing at a giventime to optimize the system with respect to a given objective function.This radar and communication system is designed to act in complimentaryfashion. Information available from radar may be used for improvingcommunication performance and vice versa.

A shared radar and communication system for a vehicle in accordance withan embodiment of the present invention includes the use of samesignaling schemes for both radar operation and communication ofinformation bits.

In an aspect of the invention, a PMCW-based signaling scheme transmitsinformation by the choice of spreading code used. In accordance withanother aspect of the invention, the information bits are modulated ontop of the spreading code.

A shared radar and communication system for a vehicle in accordance withan embodiment of the present invention includes at least onetransmitter, at least one receiver, at least one antenna, a memory, anda control processor. The at least one transmitter is configured forinstallation and use on a vehicle. The at least one transmitter isoperable to or configured to transmit a radio signal. The transmittedradio signal is generated by up-converting a baseband transmittedsignal. The baseband signal is modulated with desired information bits.The at least one receiver is configured for installation and use on thevehicle and is operable to or configured to receive a reflected radiosignal. The reflected radio signal is the transmitted radio signal(s)reflected from an object or multiple objects. The at least one receiveris also operable to or configured to receive radio signals transmittedby other similar systems. The radar system includes one or morereceivers. In each receiver, the received radio signal is down-converted(with in-phase and quadrature signals), and then sampled and quantizedusing an analog-to-digital converter (ADC) to produce possibly complexbaseband samples. The resulting complex signal from the ADC is processedby a digital processor. The control processor is operable to orconfigured to change the characteristics of the transmitted signal andto change the way the receiver processes the reflected radio signal togenerate estimates of range, velocity, and angle of objects in theenvironment and at the same time enable communications with othersimilar systems. The change of the characteristics can be in response to(i) radar detection information, (ii) information received overcommunications with other similar systems, and (iii) in response toinformation available from external devices, such as a vision-basedsystem.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an automobile equipped with a shared radar andcommunication system, in accordance with the present invention;

FIG. 2A and FIG. 2B are block diagrams of a single transmitter andreceiver in a shared radar and communications system, in accordance withthe present invention;

FIG. 3 is a block diagram of a plurality of receivers and a plurality oftransmitters (MIMO) in a shared radar and communication system, inaccordance with the present invention;

FIG. 4 is a block diagram of a single receiver and a single transmitter,in accordance with the present invention;

FIG. 5 is a plan view of an environment illustrating multiple vehiclesequipped with shared radar and communications systems operating in thatenvironment, in accordance with the present invention;

FIG. 6 is a graph illustrating an exemplary transmitted signal of aspreading code used in a PMCW radar and used to transmit informationbits, in accordance with the present invention;

FIG. 7 is a block diagram illustrating an exemplary spreading codegenerator that uses information bits to generate a spreading code, inaccordance with the present invention;

FIG. 8 is a block diagram illustrating an exemplary bank of correlatorsused for both radar detection and information bit extraction, inaccordance with the present invention;

FIG. 9 is a graph illustrating signal peak of a reflected signal whencorrelated with a known transmitted spreading code, in accordance withthe present invention;

FIG. 10 is a diagram illustrating an exemplary process for tracking andextracting information bits where either the transmitting system or thereceiving system, or both are moving, in accordance with the presentinvention;

FIG. 11 is a block diagram illustrating an exemplary data blockstructure, in accordance with the present invention; and

FIG. 12 is a plan view of an environment illustrating the exploitationof directionality to focus beams for better communication, in accordancewith the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to theaccompanying figures, wherein numbered elements in the following writtendescription correspond to like-numbered elements in the figures. Methodsand systems of the present invention achieve radar and communicationcapabilities on a same system. Radar signaling is based on signals whichhave good auto and cross correlation properties. Information bits areencoded into these signals while maintaining the same correlationproperties.

There are several types of signals used in different types of radarsystems. One type of radar signal is known as a frequency-modulatedcontinuous waveform (FMCW). In an FMCW radar system, the transmitter ofthe radar system sends a continuous signal in which the frequency of thesignal varies. This is sometimes called a chirp radar system. Mixing(multiplying) the reflected wave from an object with a replica of thetransmitted signal results in a CW signal with a frequency thatrepresents the distance between the radar transmitter/receiver and theobject. By sweeping up in frequency and then down in frequency, theDoppler frequency can also be determined.

Another type of radar signal is known as a phase-modulated continuouswaveform (PMCW). For this type of radio signal, the phase of thetransmitted signal is modulated according to a certain pattern or code,sometimes called the spreading code, known at the PMCW radar receiver.The transmitted signal is phase modulated by mixing a baseband signal(e.g., with two values +1 and −1) with a local oscillator to generate atransmitted signal with a phase that is changing corresponding to thebaseband signal (e.g., +1 corresponding to a phase of 0 radians and −1corresponding to a phase of π radians). For a single transmitter, asequence of phase values that form the code or spreading code that hasgood autocorrelation properties is required so that ghost objects areminimized. The rate at which the phase is modulated determines thebandwidth of the transmitted signal and is called the chip rate.

In a PMCW radar system, the receiver performs correlations of thereceived signal with time-delayed versions of the transmitted signal andlooks for peaks in the correlation. The time-delay of the transmittedsignal that yields peaks in the correlation corresponds to the delay ofthe transmitted signal when reflected off an object. The distance to theobject is found from that delay and the speed of light.

A radar system utilizes one or more transmitters to transmit signals.These signals are reflected from objects (also known as targets) in theenvironment and received by one or more receivers of the radar system. Atransmitter-receiver pair is called a virtual radar (or sometimes avirtual receiver).

The transmitted radio signal from each radar transmitter consists of abaseband transmitted signal, which is up-converted to an RF signal by anRF upconverter. The up-converted RF signal may be obtained by mixing thebaseband transmitted signal with a local oscillator signal at a carrierfrequency. The baseband transmitted signal used for transmission by onetransmitter of the radar system might be phase modulated using a seriesof codes. These codes, for example, consist of repeated sequences ofrandom or pseudo-random binary values for one transmitter, e.g., (−1,−1, −1, −1, 1, 1, 1, −1, 1, 1, −1, −1, 1, −1, 1), although any sequence,including non-binary sequences and non-periodic sequences could be usedand different sequences could be used for phase modulating the outputsof different transmitters. Each value of the phase modulation codesequence is often called a chip. A chip would last a certain durationcalled the chip time. The inverse of the chip time is the chip rate.That is, the chip rate is the number of chips per second. In anexemplary aspect of the present invention, the sequences of randombinary values may be provided by a truly random number generator. Atruly random number generator is explained in more detail in U.S. Pat.No. 9,575,160, which is hereby incorporated by reference herein in itsentirety. The random bit stream (with values +1 or −1) from the trulyrandom number generator may be multiplied with an output of pseudorandombinary values from a pseudorandom number generator (PRNG).

The transmitted radio signals are reflected from objects in theenvironment and are received back at the radar receivers (or virtualreceivers). Each object in the environment may reflect the transmittedradio signal. The received radio signal at the radar system wouldconsist of the sum of the radio signals reflected from various objects(targets) in the environment. In addition, a second radar systemoperating in the vicinity of the first radar system will generate atransmitted radio signal that may be received by the first radar systemand interfere with the reflected radio signals from the first radarsystem. In other words, the first radar system would receive radiosignals that include radio signals from transmitters of the first radarsystem that are reflected from objects in the environment, as well asradio signals transmitted by one or more other radar systems.

At the receiver (receive pipeline) of the radar system, the receivedradio signal is down-converted by typical amplification, filtering, andmixing with in-phase and quadrature-phase components of an oscillator.The output after down-conversion and sampling is a sequence of complexvalue digitized samples comprising a mathematical real component and amathematical imaginary component that are provided to a processor. Thebaseband signals used at the transmitter and the reflected radio signalsafter down-conversion in the receiver are provided to correlators. Thecomplex valued digitized samples at the output of the down-converter arecorrelated with various time-delayed replicas of the basebandtransmitted signals for different receivers to produce complexcorrelation values over a certain duration. That is, a sequence ofdigitized samples that correspond to a certain time duration of thereceived signal are correlated with a time-delayed replica of thebaseband transmitted signal. The process is repeated for subsequentsamples, thus producing a sequence of complex correlation values for agiven time-delay. This process is also performed for differenttransmitter/receiver pairs (virtual receivers).

A selected correlator that has a replica that is matched in delay to thetime delay of the reflected radio signal from an object will produce alarge magnitude complex correlator output. A single correlator willproduce a sequence of correlator outputs that are large if the reflectedsignal has a delay that matches the delay of the replica of the basebandtransmitted signal. If the velocity of the radar system is differentfrom the velocity of the object causing the reflection, there will be aDoppler shift in the frequency of the reflected signal relative to thetransmitted signal. A sequence of correlator outputs for one particulardelay corresponding to an object moving in the environment will havecomplex values that rotate at a rate related to the Doppler shift. Usinga sequence of correlator outputs (also referred to as a scan), theDoppler shift may be estimated, and thus the velocity of the object inthe environment determined. The longer the sequence of correlatoroutputs used to estimate the Doppler frequency, the greater the accuracyand resolution of the estimation of the Doppler frequency, and thus thegreater the accuracy in estimating the velocity of the object.

The correlation values for various time delays and various virtualradars are arranged in two-dimensional arrays known as time slices. Atime slice is a two-dimensional array with one dimension correspondingto delay or range bin and the other dimension corresponding to thevirtual radar (transmitter-receiver pair). The samples are placed intorespective range bins of the two-dimensional array (as used herein, arange bin refers to a distance range corresponding to a particular timedelay corresponding to the round-trip time of the radar signal from atransmitter, to the target/object, and back to the receiver). Thevirtual receivers of the radar system define one axis of thetwo-dimensional time slice and the range bins define the second axis ofthe two-dimensional time slice. Another new time slice comprisingcomplex correlation values is generated every 2-30 microseconds. Over alonger time interval, herein referred to as a “scan” (typically, in aduration of 1-60 milliseconds or longer), multiple time slices areaccumulated to form a three-dimensional radar data cube. One axis ordimension of the three-dimensional radar data cube is defined by time(of each respective time slice requiring 2-30 microseconds), while thereceivers (or virtual radar) define a second axis of thethree-dimensional radar data cube, and the range bins and theircorresponding time delays define a third axis of the three-dimensionalradar data cube. A radar data cube may have a preselected or dynamicallydefined quantity of time slices. For example, a radar data cube mayinclude 100 time slices or 1000 time slices of data. Similarly, a radardata cube may include different numbers of range bins. The optimized useof radar data cubes is described in detail in U.S. Pat. No. 9,599,702,which is hereby incorporated by reference herein in its entirety.

A single correlator output corresponding to a particular range bin (ordelay) is a complex value that corresponds to the sum of productsbetween a time-delayed replica of the baseband transmitted signal—with atime-delayed replica corresponding to each range bin—and the receiveddown-converted complex samples. When a particular time-delayed replicain a particular range bin correlates highly with the received signal, itis an indication of the time delay (i.e., range of the object) for thetransmitted radio signal that is received after the transmitted radiosignal reflects from an object. Multiple correlators produce multiplecomplex correlation values corresponding to different range bins ordelays. As discussed herein, each time slice contains one correlationvalue in a time series of correlation values upon which Dopplerprocessing is performed (e.g., Fast Fourier Transform). In other words,a time series of complex correlation values for a given range bin isused to determine the Doppler frequency and thus the velocity of anobject in the range bin. The larger the number of correlation values inthe time series, the higher the Doppler resolution. A matched filter mayalso be used to produce a set of outputs that correspond to thecorrelator outputs for different delays.

There may be scans for different correlators that use replicas of thetransmitted signal with different delays. Because there are multipletransmitters and multiple receivers, there may be correlators thatprocess a received radio signal at each receiver that are matched to aparticular transmitted radio signal by a particular transmitter. Eachtransmitter-receiver pair is called a “virtual radar” (a radar systempreferably has 4 virtual radars, or more preferably 32 virtual radars,and most preferably 256 or more virtual radars). The receive pipeline ofthe radar system will thus generate a sequence of correlator outputs(time slices) for each possible delay and for each transmitter-receiverpair. This set of data is called a radar data cube (RDC). The delays arealso called range bins. The part of the radar data cube for one point inthe sequence of correlator outputs is called a time slice, and itcontains one correlator output for each range bin andtransmitter-receiver pair combination.

The complex-valued correlation values contained in a three-dimensionalradar data cube may be processed, preferably by a processor establishedas a CMOS processor and coprocessor on a semiconductor substrate, whichis typically a silicon substrate. In one embodiment, the processorcomprises fixed function and programmable CPUs and/or programmable logiccontrols (PLCs). Preferably, the system will be established with a radarsystem architecture (including, for example, analog RF circuitry for theradar, processor(s) for radar processing, memory module(s), and otherassociated components of the radar system) all on a common semiconductorsubstrate. The system may preferably incorporate additional processingcapabilities (such as, for example, image processing of image datacaptured by one or more vehicle cameras such as by utilizing aspects ofthe systems described in U.S. Pat. Nos. 5,877,897; 5,796,094; 6,396,397;6,690,268 and 5,550,677, which are hereby incorporated herein byreference in their entireties) within the same semiconductor substrateas well.

The ability of a continuous wave radar system to distinguish multipletargets is dependent upon the radar system's range, angle, and Dopplerresolutions. Range resolution is limited by a radar's bandwidth (i.e.,the chip rate in a phase modulated continuous wave radar), while angleresolution is limited by the size of the antenna array aperture.Meanwhile, increasing Doppler resolution only requires a longer scan. Ahigh Doppler resolution is very valuable because no matter how close twoobjects or targets are to each other, as long as they have slightlydiffering radial velocity (their velocity towards or away from the radarsystem), they can be distinguished by a radar system with a sufficientlyhigh enough Doppler resolution. As discussed herein, the detection ofobjects with a PMCW radar system may be adversely effected by the nearbyoperation of one or more frequency modulated continuous wave (FMCW)radar systems.

The radar sensing system of the present invention may utilize aspects ofthe radar systems described in U.S. Pat. Nos. 9,846,228; 9,806,914;9,791,564; 9,791,551; 9,772,397; 9,753,121; 9,599,702; 9,575,160;9,689,967; and/or 9,869,762, and/or U.S. Publication Nos.US-2017-0309997; and/or US-2017-0307728, and/or U.S. patent applicationSer. No. 15/496,038, filed Apr. 25, 2017, Ser. No. 15/689,273, filedAug. 29, 2017, Ser. No. 15/892,764, filed Feb. 9, 2018, Ser. No.15/893,021, filed Feb. 9, 2018, and/or Ser. No. 15/892,865, filed Feb.9, 2018, and/or U.S. provisional applications, Ser. No. 62/486,732,filed Apr. 18, 2017, Ser. No. 62/528,789, filed Jul. 5, 2017, Ser. No.62/573,880, filed Oct. 18, 2017, Ser. No. 62/598,563, filed Dec. 14,2017, and/or Ser. No. 62/623,092, filed Jan. 29, 2018, which are allhereby incorporated by reference herein in their entireties.

FIG. 1 illustrates an exemplary radar/communications system 100configured for use in a vehicle 150. In an aspect of the presentinvention, a vehicle 150 may be an automobile, truck, or bus, etc. Asillustrated in FIG. 1 , the radar/communications system 100 may compriseone or more transmitters and one or more receivers 104 a-104 d for aplurality of virtual receivers. Other configurations are also possible.As illustrated in FIG. 1 , the radar/communications system 100 maycomprise one or more receivers/transmitters 104 a-104 d, control andprocessing module 102 and indicator 106. Other configurations are alsopossible. FIG. 1 illustrates the receivers/transmitters 104 a-104 dplaced to acquire and provide data for object detection and adaptivecruise control. In addition, these transmitters/receivers can alsocommunicate information bits to other systems mounted on a differentvehicle. The radar/communications system 100 (providing such objectdetection and adaptive cruise control or the like) may be part of anAdvanced Driver Assistance System (ADAS) for the automobile 150. Thecommunication with other adjacent vehicles may allow additionalinformation, available to the adjacent vehicle but not to automobile150, to be available at automobile 150 for better ADAS performance,which is otherwise not visible to it.

There are several ways to implement a shared radar and communicationsystem. One way, shown in FIG. 2A uses a single antenna 202 fortransmitting and receiving. The antenna is connected to a duplexer 204that routes the appropriate signal from the antenna to the receiver 208or routes the signal from the transmitter 206 to the antenna 202. Acontrol processor 210 controls the operation of the transmitter andreceiver and estimates the range and velocity of objects in theenvironment. The control processor is also responsible for modulatingany desired information bit for transmission as well for decoding anyinformation bits transmitted from other similar systems. A second way toimplement a radar system is shown in FIG. 2B. In this system, there areseparate antennas for transmitting (202A) and receiving (202B). Acontrol processor 210 performs the same basic functions as in FIG. 2A.In each case, there may be a display 212 that receives displayinformation from the control processor 210 to display or visualize thelocation of objects in the environment and the information obtained fromother systems.

An exemplary shared radar and communications system 300 with multipleantennas, transmitters, and receivers (MIMO) is illustrated in FIG. 3 .Using multiple antennas allows a MIMO system to determine the angle(azimuth or elevation or both) of targets/objects in the environment.Depending on the geometry of the antenna system, different angles (e.g.,azimuth or elevation) can be determined. A MIMO configuration alsoallows the system to determine the angle of any other system that it iscommunicating with. The MIMO system can then focus on that particularangle for communicating with the remote system.

The shared radar and communications system 300 may be connected to anetwork via an Ethernet connection or other types of network connections314. The system 300 will have memory (310, 312) to store software usedfor processing the signals in order to determine range, velocity andlocation of objects. The software also performs necessary operations tomodulate the information bits onto the radar signal as well asextracting information bits embedded in the radar signals from othersimilar systems. Memory can also be used to store information abouttargets in the environment.

A basic block diagram of a PMCW system with a single transmitter andreceiver is illustrated in FIG. 4 . The transmitter 400, illustrated inFIG. 4 , consists of a digital processing block 410, followed by adigital-to-analog converter (DAC) 420. The digital processing block 410,also known as a digital signal generator 410, is capable of acceptingexternal information bits and modulating them onto the transmittedsignal. The output of the DAC 420 is up-converted to a radio frequency(RF) signal and amplified by an analog processing unit 430. The resultis then output to the input of the antenna 440. The digital signalgenerator 410 generates a baseband signal. The receiver 450, illustratedin FIG. 4 , consists of a receiving antenna 460, an analog processingunit 470 that down amplifies the signal and mixes the signal tobaseband. This is followed by an analog-to-digital converter (ADC) 480and then digital baseband processing 490. There is also a controlprocessor (illustrated as the control & processing block 210 in FIGS. 2Aand 2B) that controls the operation of the transmitter 400 and receiver450. The baseband processing will process the received signal and maygenerate data that can be used to determine range, velocity, and angle.The baseband processing will also process any information bits that needto be communicated and/or any signals received from other systems thathave information contained in the signals.

It is possible to use the concept described herein with various meansfor modulating the data onto a transmitted signal. For example, it ispossible to use a variety of modulation techniques including Gaussianminimum shift keying (GMSK) modulation scheme which provides bettercontrol of the power spectrum of the output signal. In anotherembodiment, an orthogonal frequency division multiplex (OFDM)-basedmodulation scheme, which spreads the information into the time-frequencyplane can be used for a shared use of radar detection and communication.

FIG. 5 illustrates one way in which vehicles equipped with such a sharedradar and communication system can provide better performance than asimple radar system. Vehicles 501-504 are equipped with systemsaccording to the present invention. Vehicle 501 can detect andcommunicate with vehicles 502-503 but cannot detect nor communicate withvehicle 504 due to an obstacle (such as building 505) at thecross-section. However, vehicle 503 can detect and communicate withvehicle 504. Vehicle 503 can then communicate to vehicle 501 thelocation and presence of vehicle 504 at the crossroad. This will allowvehicle 501's ADAS system to make a better decision. Other scenarios areeasy to imagine. If vehicle 502 is instead directly in front of vehicle501, vehicle 502 could block the view of vehicle 503 from the radarsystem in vehicle 501. The information about vehicle 503 could becommunicated from vehicle 502 back to vehicle 501.

As mentioned herein, there are various types of signals used in radarsystems. One type of continuous wave radar signal is known asphase-modulated continuous-wave (PMCW). The phase of the transmittedsignal is varied in PMCW systems. Often, the variation of the phase isaccording to a spreading code. The spreading code may be binary (e.g.,+1 and −1), in which case the phase of the transmitted signal at anytime takes on one of two possible values (e.g., 0 and π radians).Spreading codes with more than two levels can also be used. Often, thecode repeats after a certain time duration, sometimes called the pulserepetition interval (PRI). Various types of spreading codes can be used.These include pseudorandom binary sequence (PRBS) codes also calledm-sequences, almost perfect autocorrelation sequences (APAS), Golaycodes, constant amplitude zero autocorrelation codes (CAZAC), also knownas Frank-Zadoff-Chu (FZC) sequences, as well as many other codes thatcan be used. In a radar system with a single antenna, a single spreadingcode is used. The autocorrelation of this single code determines thecapability of the radar to estimate the range (range resolution andmaximum unambiguous range).

In a multiple-input, multiple-output (MIMO) system, there are multipletransmitters that operate simultaneously. Each transmitter uses aspreading code and thus multiple codes are needed, one for eachtransmitter. In this case (multiple transmitters), codes that have goodautocorrelation, as well as good cross-correlation properties aredesirable. Generally, the better the autocorrelation of codes, the worsethe cross-correlation properties.

Systems with multiple transmitters can also be used to transmit the samespreading code. In this case, by controlling the phase of eachtransmitter, one can transmit more power in a given direction. This isknown as phased array beamforming in the industry.

In order to achieve communication shared with radar communication,information bits can be incorporated into the spreading codes (formodulating a transmit signal) in various ways. In one preferredembodiment, information bits are modulated on the transmit signal on aspreading code basis. In this case, one can choose any of the codesmentioned earlier, e.g., almost perfect autocorrelation sequences(APAS), Golay codes, constant amplitude zero autocorrelation codes(CAZAC), or m-sequences. FIG. 6 illustrates an example of such a binary(two-valued) spreading code: an m-sequence with length 31 (601). Fivesuch code sequences are shown. Sequence 602 illustrates the waveform forinformation bit sequence “11010”. The first two sequences and the fourthsequence are modulated with bit “1” and are thus sent as is. The thirdand the fifth sequence are modulated with bit “0” and hence signinversed. After comparing the received signal from a remote radar systemand correlating with the corresponding sequence, the system candetermine which of the information bits (“0” or “1”) has been used tomodulate the spreading code. In this case, the receiver needs knowledgeof the codes used at the transmitter.

In a preferred embodiment, the information bits are directly modulatedonto the spreading codes. Alternatively, the information bits canthemselves be used to generate the spreading code. As illustrated inFIG. 7 , the information bits are passed through a scrambler 701. Theinformation bits can be used as the initial state of an m-sequencegenerator. A typical scrambler uses a linear feedback shift register(LFSR) circuit that generates a sequence depending on the initial stateand the feedback connections. The information bits can be used to decideon the initial state or the information bits can be used to decide thefeedback connections used. The output has the properties of a PRBSsequence with good auto and cross-correlation properties. If theinformation bits are directly modulated onto the spreading codes, theinformation bits can be recovered from the received signal if theinitial state and specific properties of the LFSR are known to thereceiver. If the information bits are used to select a spreading orscrambling code, then correlators with various possible spreading codesare used to recover the information bits at the receiver. The output ofthe scrambler 701 can also be used as the spreading code for radartransmission. Another technique that can be used to transmit informationis done using orthogonal frequency division multiplexing (OFDM). In thiscase, multiple carriers are used to transmit information. As is wellknown, OFDM can use an inverse Fourier transform to generate a timedomain signal for transmission and then at the receiver use a Fouriertransform to recover the information. Different information can betransmitted on different frequencies, or the information can be encodedwith an error control code, and then the coded information can betransmitted on different frequencies.

Before modulation, the information bits can be differentially encoded.This means that instead of sending the bits themselves, the differenceof a current bit to a previous bit is sent. Mathematically, thisoperation is equivalent to d_(k)=b_(k) ⊕b_(k-1), where ⊕ represents aBoolean XOR operation. This makes the communication system robust toconstant phase rotation, such as what might be experienced as thetransmitter and the receiver are not moving at a same velocity.

As illustrated in FIG. 4 , the received signal is down-converted to acomplex baseband signal via an RF front end analog signal processingblock 470. The analog signal processing involves amplification, mixingwith a local oscillator signal, and filtering. The mixing is with twosinusoidal signals that are 90 degrees out of phase (e.g., cosine andsine, or in-phase and quadrature-phase signals). After down-conversion,the complex analog baseband signal is converted to a complex basebanddigital signal using analog-to-digital converters (ADCs) 480. Thecomplex baseband digital signal (output by the ADCs 480) is then theinput to a digital processing unit 490.

The complex baseband output consists of two aspects of the signal. Afirst aspect includes reflections from objects that are copies of thetransmitted signal. A second aspect includes information bits that aretransmitted by other systems. For example, in FIG. 5 , the combinedradar and communications system in vehicle 501 receives reflections ofits own transmitted signal from vehicle 502-503. In addition, thecombined radar and communications system has also received signalstransmitted by the combined radar and communications systems in vehicles502-503.

Referring to FIG. 4 , the digital processing block 490 performscorrelations or matched filtering. The correlators multiply the receivedcomplex baseband signal by a delayed replica of the baseband transmittedsignal. The result is accumulated over a certain time interval. Asillustrated in FIG. 8 , a bank of correlators 810, where each correlator810 has a different delay used for the replica of the basebandtransmitted signal, will produce a set of correlations that correspondto different ranges of objects. In essence, a correlator that has aparticular delay of the baseband transmitted signal is looking for thepresence of a reflection from an object at a distance corresponding tothe particular delay for the particular correlator, and for which theround-trip delay is the delay used for the baseband transmitted signal.Such a peak is illustrated in FIG. 9 , where the peak in the matchedfilter output represents an object at the distance of reflection. Thecross correlation between those signals with its own transmitted signal,and those transmitted by others, will be low and thus only reflectedsignals will show the peak.

In one preferred embodiment, the information bits are transmitted basedon the scheme illustrated in FIG. 6 . The correlator 810 performs acorrelation with a replica of the spreading code used by the remotetransmitting system. The value at the peak will correspond to the bitsent (potentially rotated by some phase depending on the channel betweenthe transmitter system and the receiver system). An initial search maybe needed to locate the peak across delayed replicas of the spreadingcode used by the transmitter. Once the peak is found, the receiver willcontinue to calculate the correlation with +/−1 delay from the peak.This is illustrated in FIG. 10 . 1001 is the case when a peak has beenfound and data is decoded from the peak. However, the two neighboringdelays are being monitored. As the vehicles move, the peak will movefrom one delay to the next. 1002 shows the case during cross-over. Thedata can be decoded from the larger of the peaks or from an averagevalue on the two peaks. 1003 is the case when data is now recovered forthe peak at a new location and the two new neighboring delays aremonitored. This embodiment requires that the receiver has knowledge ofthe spreading code used by the transmitter of the other system.

In another preferred embodiment, the information bits are transmittedbased on the scheme illustrated FIG. 7 . Here, the data is directlyrecovered from the ADC samples. In case of a differentially encodedcase, the phase differences of the ADC samples are used to recover thedata. This embodiment requires a higher SNR than the one describedearlier. However, the radar reflection signals cover twice the distancefrom that of the signal from a remote object at the same distance andhence, the signal with information bits to be decoded is expected to beat a much higher signal level than the reflected own signals used forradar detection.

The information bits can be arranged in blocks as illustrated in FIG. 11. The block size is determined based upon a frequency and timing offsetbetween the transmitter and receiver system. The block of FIG. 11 isprepended with start bits (also known as a preamble) comprising a knownbit sequence that can be used to determine the start of the block at thereceiver. In the case of a signaling scheme illustrated in FIG. 6 , thestart bits can be modulated with the same and a known spreading code foreasier detection. As an exemplary embodiment, a preamble size of 16 bitsand a block size of 100 information bits are used.

The system can be enhanced through the use of various channel codingsystems as are known in the industry. The channel coding mechanism caninclude simple repetition coding, where the same data block is repeatedseveral times, or more advanced channel coding schemes likeconvolutional coding, block coding, turbo coding, or low density paritycheck coding.

The description herein includes a shared radar and communication systemin which there are N_(T) transmitters and N_(R) receivers. For radardetections, this results in N_(T)×N_(R) virtual radars, one for eachtransmitter-receiver pair. For example, a radar system with eighttransmitters and eight receivers will have 64 pairs or 64 virtual radars(with 64 virtual receivers). This set of virtual receivers can be usedto determine the angle of arrival (AOA) of reflection signals. Forcommunication, only the N_(R) receivers can be used to determine the AOAof the received signal. These N_(R) receivers can then be used to focusthe signal reception in the given direction to increase a signal level.The N_(T) transmitters can also be used to focus the transmitted signalin any desired direction. This is illustrated in FIG. 12 . Theinformation exchanged between vehicle 1201 and 1202 is done withfocusing the signal transmission and reception directions in thedirection of each other.

If the multiple transmitters and the multiple receivers are used tofocus (beam form) information bit transmission and reception in a givendirection, the radar detection can only be done in the region covered bythe signal transmission. In one preferred embodiment, the shared radarand communication system takes a time division multiplexing approach. Inthis method, the system alternately uses a broad transmission for radardetection and a narrow focused transmission for communications. Inanother preferred embodiment, the system allocates a subset oftransmitters and receivers for broad transmission used in radardetection and a different subset for narrow focused transmission usedfor communication. In this case, radar detection and communications canbe carried out simultaneously.

The system can analyze the radar detection data to analyze the potentialsources of other systems to be communicated with and design transmissionparameters such as transmission direction and power, and necessarycoding based on location(s) of the remote systems. The system can alsotake data from external sources, such as: camera based systems, and aGPS map to analyze potential sources to be communicated with andoptimize thereof.

The information available from other vehicles received over acommunication channel can also be used to optimize operations of theradar in a shared radar and communications system. If an advancedknowledge of locations with vulnerable road users (VRU), such aspedestrians, is available to a vehicle not yet visible in a radarscreen, the system can design radar scans optimized to identify theactivities of such VRU beforehand.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the presentinvention, which is intended to be limited only by the scope of theappended claims, as interpreted according to the principles of patentlaw including the doctrine of equivalents.

The invention claimed is:
 1. A shared radar sensing and communicationssystem for a vehicle, the system comprising: a transmitter configured tomodulate radio signals based on a first spreading code, wherein thefirst spreading code is defined at least in part by a first plurality ofinformation bits, wherein the first plurality of information bitsencodes selected information, wherein the transmitter is furtherconfigured to modulate the radio signals based on a second spreadingcode before modulating the radio signals based on the first spreadingcode, wherein the transmitter is configured to further modulate themodulated radio signals based on the first spreading code to producefirst modulated radio signals, wherein the transmitter is configured toproduce the first modulated radio signals based on both the firstspreading code and the second spreading code, and wherein thetransmitter is configured to transmit the first modulated radio signals;and a receiver configured to receive: a first radio signal that includesthe transmitted radio signals transmitted by the transmitter andreflected from objects in an environment, wherein said receiver isoperable to process the first radio signal to detect objects in theenvironment; and a second radio signal transmitted from another system,wherein said second radio signal carries a second plurality ofinformation bits, wherein said receiver is operable to process thesecond radio signal to determine the second plurality of informationbits, and wherein the second plurality of information bits are encodedwith information selected by the other system.
 2. The shared radarsensing and communications system of claim 1, wherein the firstplurality of information bits are mapped to one of +1 and −1, and usedto modulate or multiply the radio signals.
 3. The shared radar sensingand communications system of claim 1, wherein the first plurality ofinformation bits are arranged in a block structure with a series ofpreamble bits followed by a finite quantity of information bits.
 4. Theshared radar sensing and communications system of claim 3, wherein alength of the block structure is determined by a frequency and timingoffset between the transmitter and another radar sensing systemreceiving the transmitted radio signals modulated by the secondspreading code.
 5. The shared radar sensing and communications system ofclaim 1, wherein the other system is another radar sensing system. 6.The shared radar sensing and communications system of claim 5, whereinthe first plurality of information bits carries information related toat least one object that is detected by the receiver and is not detectedby the other radar sensing system.
 7. The shared radar sensing andcommunications system of claim 1 further comprising a plurality oftransmitters, wherein a first subset of transmitters of the plurality oftransmitters are used in the detection of objects in the environment,and wherein a second subset of transmitters of the plurality oftransmitters are used to communicate information bits to another radarsensing system.
 8. The shared radar sensing and communications system ofclaim 7, wherein the second subset of transmitters of the plurality oftransmitters is configured to transmit with a narrowed focus in adirection of the other radar sensing system, and wherein the firstsubset of transmitters of the plurality of transmitters is configured totransmit with a broad focus away from the equipped vehicle.
 9. Theshared radar sensing and communications system of claim 7 furthercomprising a plurality of receivers, wherein a first subset of receiversof the plurality of receivers are used in the detection of objects inthe environment, and wherein a second subset of receivers of theplurality of receivers are used to receive the second plurality ofinformation bits from the other transmitter.
 10. The shared radarsensing and communications system of claim 1, wherein the secondplurality of information bits carries information related to at leastone object that is not detected by the receiver and that is detected bythe other system.
 11. The shared radar sensing and communications systemof claim 10 further comprising a display, wherein the display isconfigured to display information related to the at least one objectthat is not detected by the receiver but that is detected by the othersystem.
 12. A method for managing a shared radar sensing andcommunications system, the method comprising: providing a transmitterconfigured to modulate radio signals based on a first spreading code,wherein the first spreading code is defined at least in part by a firstplurality of information bits, and wherein the radio signals to bemodulated based on the first spreading code were previously modulatedbased on a second spreading code, and wherein the modulated radiosignals are further modulated based on the first spreading code toproduce first modulated radio signals, wherein the first modulated radiosignals are based on both the first spreading code and the secondspreading code; selecting the first plurality of information bits toencode selected information for transmission; transmitting the modulatedradio signals with the transmitter; providing a receiver configured toreceive: a first radio signal that includes the transmitted radiosignals transmitted by the transmitter and reflected from objects in anenvironment; and a second radio signal transmitted from another system,wherein said second radio signal carries a second plurality ofinformation bits; processing, with the receiver, the first radio signalto detect objects in the environment; and processing, with the receiver,the second radio signal to determine the second plurality of informationbits, and wherein the second plurality of information bits are encodedwith information selected by the other system.
 13. The method of claim12 further comprising sequentially receiving, with the receiver, boththe first radio signal and the second radio signal.
 14. The method ofclaim 13, wherein the first plurality of information bits carriesinformation related to at least one object that is detected by thereceiver and is not detected by the other system.
 15. The method ofclaim 14, wherein the other system is another radar sensing system. 16.The method of claim 12, wherein the second plurality of information bitscarries information bits related to at least one object that is notdetected by the receiver and that is detected by the other system. 17.The method of claim 16 further comprising providing a display configuredto display information related to the at least one object that is notdetected by the receiver but that is detected by the other system. 18.The method of claim 12 further comprising providing a plurality oftransmitters, wherein a first subset of transmitters of the plurality oftransmitters are used in the detection of objects in the environment,and wherein a second subset of transmitters of the plurality oftransmitters are used to communicate information bits to the othersystem.
 19. The method of claim 18 further comprising: transmitting,with the first subset of transmitters, in a narrowed focus in adirection of the other system; and transmitting, with the second subsetof transmitters, in a broad focus away from an equipped vehicle.
 20. Themethod of claim 12 further comprising providing a plurality ofreceivers, wherein a first subset of receivers of the plurality ofreceivers are used in the detection of objects in the environment, andwherein a second subset of receivers of the plurality of receivers areused to receive the second plurality of information bits from the othertransmitter.